The present invention relates to II-VI semiconductor devices such as light emitting diodes and laser diodes. More specifically, the present invention relates to a II-VI semiconductor device having reduced stacking fault defects.
Group II-VI compound semiconductor devices are known. Such devices are useful in constructing light emitting or detecting devices, diodes and laser diodes such as those described in U.S. Pat. No. 5,213,998, issued May 25, 1993; U.S. Pat. No. 5,248,631, issued Sep. 28, 1993; U.S. Pat. No. 5,274,269, issued Dec. 28, 1993; U.S. Pat. No. 5,291,507, issued Mar. 1, 1994; U.S. Pat. No. 5,319,219, issued Jun. 7, 1994; U.S. Pat. No. 5,395,791, issued Mar. 7, 1995; U.S. Pat. No. 5,396,103, issued Mar. 7, 1995; U.S. Pat. No. 5,404,027, issued Apr. 4, 1995; U.S. Pat. No. 5,363,395, issued Nov. 8, 1994; U.S. Pat. No. 5,515,393, issued May 7, 1996; U.S. Pat. No. 5,420,446, issued May 30, 1995; U.S. Pat. No. 5,423,943, issued Jun. 13, 1995; U.S. Pat. No. 5,538,918, issued Jul. 23, 1996; and U.S. Pat. No. 5,513,199, issued Apr. 30, 1996.
Historically, diodes have generated red or infrared light. However, there are many applications where diodes that emit radiation in shorter wavelengths, for example, in the blue and green portions of the spectrum (i.e., at wavelengths between 590 nm and 430 nm) would be useful. Further, such short wavelength laser diodes would increase the performance and capabilities of many existing systems that currently use infrared and red laser diodes.
Currently, II-VI (ZnSe-based) laser diodes and light emitting diodes grown on GaAs wafers suffer from stacking fault defects that originate at the interface between the III-V material and the II-VI material. These defects extend up through the laser stack and intersect the active (light-generating) region. This intersection is a site for the generation of mobile point defects in the material. These defects appear as a dark spot at the start of laser operation. As laser operation continues, the dark spot grows into a dark line which, in turn, causes more dark lines to form until the device ultimately fails. Because ZnSe has a low stacking fault energy, this type of defect is difficult to avoid.
The present invention includes a II-VI semiconductor device having a stack of II-VI semiconductor layers. The stack of II-VI semiconductor layers is carried on a GaAs substrate. A BeTe buffer layer is provided between the GaAs substrate and stack of II-VI semiconductor layers. The BeTe buffer layer has a thickness of more than about 80 xc3x85 to thereby reduce stacking fault defects at the interface between the GaAs substrate and the stack of II-VI semiconductor layers.
Another aspect of the present invention includes fabricating a II-VI semiconductor device having a BeTe buffer layer positioned between the stack of II-VI semiconductor layers and the GaAs substrate. During fabrication, the BeTe buffer layer is grown to a thickness of more than about 80 xc3x85 at a temperature which is sufficiently high to ensure low defect growth initiation.